ITS and Transit
Contact lubricants increase the reliability and lifetime of all current
carrying metal interfaces Contact Lubricants Contact lubricants increase
the reliability and lifetime of all current carrying metal interfaces.
These include switches, connectors and busbars.
Electrolube has been the leading supplier of contact lubricants since
their invention by Electrolube in the 1950s. A wide range of products is
available covering all common applications, while a program of continual
development provides specialty products for ever changing customer needs.
Manufactured as tenacious greases and oils, products are available for
consistent operation at temperature extremes and with sensitive plastics
that are normally attacked by traditional lubricants.
The use of an appropriate contact lubricant will solve the problems of
wear, poor signal quality, inconsistent operation and allow the use of
less expensive materials. The choice of lubricant can also allow the
'feel' characteristics of the switch to be optimized.
How Contact Lubricants Work
Contact technology is constantly developing with new alloys, plastics and
customer demands. However, it is still impossible to solve the main cause
of switch malfunction i.e. the inability to produce a perfectly smooth
metal contact surface. This leads to the following problems:
Microscopic examination reveals peaks and troughs on the surface and when
the contacts come together, only the peaks are actually touching. The true
current carrying surface area is therefore far smaller than it would
appear. As the current is carried by a fraction of the designed surface
area, the heat generated is concentrated at the peaks. This, in turn,
causes the formation of high resistance oxide layers. As the resistance
increases, more power is converted into heat leading to further oxidation.
This spiraling effect creates hot spots reducing the efficiency of the
switch and can cause complete failure as the two surfaces weld together.
The application of an Electrolube contact lubricant solves this problem.
The lubricant film dramatically increases the effective surface area as,
in thin films, the lubricants allow the passage of electricity. The switch
now has the surface area that the designers planned. Hot spots are
eliminated and the contact resistance remains low and stable.
As un-lubricated contacts open and close, arcing (mini-lightning strikes)
will occur. Arcing is destructive as it generates heat, causing oxide
formation, and as the amount of energy is high, corrosive by-products can
be formed. These cause corrosion of the surface and can destroy plated
contacts. Ionization of the air and the associated rise in temperature
causes metal transfer between the contacts, resulting in the formation of
new "peaks and troughs" - a common problem found in high power contacts.
The problem of arcing is
compounded in "make & break" switches where every time the circuit is
operated, the contacts may bounce several times before finally mating.
This exacerbates the problems discussed previously and subjects the
circuit to repeated surges of current giving a poor signal to noise ratio.
This problem of arching is
not found in lubricated switches, as the lubricant fills the air gap
between the contacts, preventing arcing, related temperature rises and
corrosive chemical formation. As air is excluded from the metal surfaces,
airborne contamination cannot form insulative barriers on the metals.
Contact lubricants provide a cushion between the contacts to damp the
effects of bouncing.
The problems describes previously are compounded by the action of the two
surfaces rubbing against each other. This occurs in all metal interfaces,
whether static or moving. Why static contacts (connectors) suffer from
mechanical wear may not be immediately obvious. However, this phenomenon
is explained by the fact that connectors and closed contacts are exposed
to small amplitude movements caused by vibration, temperature changes etc.
These small movements are known as "frettage". As the surfaces fret,
friction causes metal particles to be removed from the peaks breaking
through plated surfaces. This exposes surface and underlying metal to the
effects of oxidation and wear. Additionally the detached metal particles
can cause intermittent signal transmission and ultimately switch failure. The lubricated switch is
subjected to far less mechanical wear as the lubricant facilitates smooth
movement. Friction is therefore greatly reduced, as is wear, extending
Gold contacts are usually thought to be inert but they can also
benefit from contact lubrication. While they do not oxidize, gold is
porous, so moisture and salts creep under the plated layer which
separates from the base metal and is easily worn away. This exposes
the base metal which may corrode or oxidize. Contact lubricants form a
protective, durable film over the porous areas, preventing the entry
of moisture and other contaminants.
The way a switch feels when operated has become an indicator of quality
particularly within the automotive industry. Contact lubricants, in
addition to their technical benefits can also determine the feel of a
switch, whether it be strong and decisive for the dashboard of a
commercial vehicle, or smooth and quiet for a luxury car.
Silicone contamination poses particular problems which can also be
overcome by contact lubricants. Silicones are found in lubricants,
sealants, polishes and mould release agents. As silicones can "creep"
great distances, these products should not be used in switch assembly
areas. When silicones are present between moving or vibrating contacts,
they react under arcing conditions to form silicon carbide. These crystals
abrade the contact surface and cause electrical breakdown. Silicone
contamination is very difficult to remove, particularly after the
formation of silicon carbide. It cannot be removed by solvents. There are
certain contact lubricants that can prevent the damage caused by silicones
and can even restore damaged contacts. One such treatment from Electrolube
reacts with the silicon carbide to form volatile silicon tetrafluoride
gas, thus slowly breaking down the hard particles.
If a contact lubricant is
used on the switch prior to the introduction of silicones these problems
Benefits of Contact Lubrication
Contact lubricants are specially formulated greases and oils that reduce
friction and enhance the electrical performance of current carrying metal
interfaces in switches and connectors. Electrolube products are
electrically insulative in thick films, preventing tracking. In ultra thin
films, i.e. between closed metal contacts, they allow the current to flow,
owing to the "Quantum Tunneling Effect". They also exhibit a neutral pH
thereby avoiding surface corrosion.
Tests have shown that contact lubrication can extend the lifetime of
switches by more than 300%, producing excellent performance under all
circumstances and preventing the need for expensive maintenance. Contact
lubricants also help to improve the reputation of manufacturers by
reducing or preventing warranty claims and associated commercial costs of
The effectiveness of even perfectly designed switches can be improved by
contact lubricants and, when considered at design stage, significant
production cost savings can be achieved by the use of less expensive
materials (both plastics and contact metals).
Domestic Switches Connectors
The range of applications is vast
and can include anything from PC edge connectors to switches in washing
machines, kettles, hair dryers and electric blankets. Contact lubricants
will bring significant benefits to any application where switches and
contacts are fundamental to successful, long term operation.
Automotive Switches Connectors
The use of contact lubricants is widespread in the automotive industry,
where they are employed to ensure reliability, safety, efficiency and to
control the feel of switches. Common uses include indicators, widows,
wipers, horns, ignition, demisters, headlights, locking systems, earthing
points and all harness connections. Electrolube contact lubricants also
have excellent mechanical lubricity. This allows their use in situations
not involving current carrying surfaces, eliminating the potential for
failure from the migration of purely mechanical lubricants onto contact
Electrolube has developed a range
of specialty lubricants that offer unrivalled performance by virtue of
their high levels of materials compatibility. This allows the use of lower
cost plastics including normally sensitive transparent grades (for
illuminated fascia switches etc). They are extensively used on rotating
shafts within switches, ventilation systems and for the lubrication of
plastic cogs and gears.
compound has been developed to prevent corrosion and contamination', and
to improve electrical contact on anode and cathode pick-up shoes, rack
contacts and busbar joints.
Electrolube's range of contact lubricants has been developed to improve
the efficiency and life-span of switches and connectors. However, it is
important to discuss options with the Electrolube team at the design stage
to ensure that the correct product is selected and properly applied. Among
the areas to be considered are voltage, current, operating temperature
range, contact metals, number of cycles and associated plastic.
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